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Supplemental Online Material
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for
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Substrate and environmental controls on microbial assimilation of
soil organic carbon: a framework for Earth system models
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Xiaofeng Xu1, Joshua Schimel2, Peter Thornton1, Xia Song1, Fengming Yuan1, Santonu
Goswami1
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1. Climate Change Science Institute and Environmental Sciences Division, Oak Ridge National
Laboratory, Oak Ridge, TN 37831, USA; 2. Department of Ecology, Evolution, and Marine Biology,
University of California, Santa Barbara, CA 93106, USA
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Correspondence: X.X. (xux4@ornl.gov)
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This file contains Table S1, Figures S1, S2, S3, S4, S5, and S6, and references.
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Table S1. Biome-level parameters and initial conditions for model simulations of microbial
assimilation of soil organic carbon
Parameters
Initial conditions
Csub (mg C Kg-1
Cmic (mg C
Biome
CNS
CNB
soil)
Kg-1 soil)
1e-10
Boreal forest
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96734
1e-10
Temperate coniferous forest
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5
44750
1e-10
Temperate broadleaf forest
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7
54568
1e-10
Tropical/subtropical forest
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8
28288
1e-10
Grassland
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6
25000
1e-10
Shrub
17
6
47960
1e-10
Tundra
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250000
Desert
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2072
1e-10
Natural wetlands
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275000
1e-10
Global average
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50000
1e-10
Note: the C:N ratio in this table is mass based, not molecular basis reported in Xu et al. (2013)
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Figure S1. Histogram of the MAAP for primary biomes (the values below the biome name
represent average and range of the MAAP at 90% confidence level; MAAP: microbial annual
active period)
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Figure S2 Spatial distribution of MAAP as estimated based on the soil temperature and moisture
simulated by Community Land Model 4.0 (MAAP: microbial annual active period)
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Figure S3 Spatial distributions of (A) average microbial activity index and (B) cumulative
microbial activity index
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Figure S4. (A) The daily soil temperature and moisture and (B) calculated CMAX and MAAP at
MAAP = 275 days and MAAP = 293 days (MAAP: Microbial Annul Active Period; CMAX:
Cumulative Microbial Activity index; CMAX is the area beneath the lines in (B))
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CESM/CLM
Model
Daily soil
temperature
and moisture
C:N
range
Adjust
temperature
and moisture to
meet MAAP
MAAP
range
Latin Hypercube
Sampling
200 pairs of
MAAP & C:N
Biome-level model simulations (200 estimates each biome)
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Biome-level microbial assimilation of soil organic
carbon (Cmic/Corg)
Figure S5. The flowchart showing the biome-level estimates Cmic/Corg (CESM: Community
Earth System Model; CLM: Community Land Model (Thornton et al., 2009))
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Figure S6. Model simulations for soil microbial biomass C driven by the globally averaged
substrate quality and daily soil temperature and soil moisture (inset shows the seasonality of
microbial biomass carbon over the last year)
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References
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1.
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Thornton, P.E., Doney, S.C., Lindsay, K., Moore, J.K., Mahowald, N.M., Randerson, J.T. et al.
(2009). Carbon-nitrogen interactions regulate climate-carbon cycle feedbacks: results from an
atmosphere-ocean general circulation model. Biogeosciences, 6, 2099-2120.
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2.
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Xu, X., Thornton, P.E. & Post, W.M. (2013). A global analysis of soil microbial biomass carbon,
nitrogen, and phosphorus in terrestrial ecosystems. Global Ecology and Biogeography, 22, 737749.
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